OMeiosis - Meiosis & Sexual Reproduction Meiosis &...

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Heyer 1 Sexual reproduction creates new combinations of alleles. Cells Arise From Preexisting Cells I. Asexual (Mitotic) Reproduction a. Mitosis : production of two identical nuclei b. Cytokinesis: physical division of the cell into two II. Sexual (Meiotic) Reproduction a. Meiosis : production of four non -identical nuclei b. Cytokinesis: physical division of the cell c. Fertilizarion: fusion of two sex cells d. Syngamy: fusion of two nuclei Diploid cells have homologous pairs of chromosomes: 1 set from mom, 1 set from dad. Homologous chromosomes: same loci, maybe different alleles. Meiosis: Reductive Division — Reduces Chromosome Number in Half V Meiosis has 2 consecutive divisions Meiosis I : Homologous pairs separate Meiosis II : Sister chromatids separate V Each division has a prophase, metaphase, anaphase and a telophase Meiosis: 2n Ë 1n Diploid Ë haploid Sex = Meiosis + Syngamy Syngamy : 1n Ë 2n Haploid Ë diploid
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Heyer 2 Sexual Life Cycles Diploid life history (animals) Haploid life history (fungi) Alternation of Generations (plants) Chromosomes Matched in Homologous Pairs V Human somatic (body) cells – 46 chromosomes, 23 pairs – Homologous = same size, shape,and genes V Pairs #1 - 22 = Autosomes – Both male and female V Pair #23 = Sex Chromosomes – Determine gender – XX = female, XY = male Human karyotype
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OMeiosis - Meiosis & Sexual Reproduction Meiosis &...

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